mediumMultiple Choice
CS0-003 Practice Question: Refer to the exhibit
Exhibit
The following output is from a compromised server: Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 10.0.0.5:3389 192.168.1.10:54321 TIME_WAIT tcp 0 0 10.0.0.5:54321 198.51.100.20:4444 ESTABLISHED tcp 0 0 10.0.0.5:22 10.0.0.1:50001 ESTABLISHED
Refer to the exhibit. An analyst reviews the output from a netstat command on a server. Which connection is MOST likely indicative of command and control (C2) activity?
⚠ Common exam trap
CompTIA often tests the candidate's ability to recognize that not all high-port connections are malicious; the trap here is that options A and D use high ephemeral ports but are normal internal administrative traffic, leading candidates to incorrectly flag them as suspicious instead of focusing on the external destination and the specific C2-associated port 4444.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
10.0.0.5:54321 to 198.51.100.20:4444
The connection from a high ephemeral port (54321) on the server to an external IP (198.51.100.20) on port 4444 is a classic indicator of C2 activity. Port 4444 is commonly associated with Metasploit's default reverse shell listener and other malware frameworks, while the use of a non-standard high source port and an external destination suggests outbound beaconing or command reception.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
10.0.0.5:22 to 10.0.0.1:50001
Why it's wrong here
This connection represents a standard SSH session where an internal host (10.0.0.5) is securely connecting to another internal host (10.0.0.1) for administrative purposes. SSH operates on the well-known port 22, and the destination port 50001 is an ephemeral port assigned to the client side of the connection, which is normal for client-initiated traffic. This is typical, legitimate management traffic within an organization's network.
- ✓
10.0.0.5:54321 to 198.51.100.20:4444
Why this is correct
This connection is highly suspicious and a strong indicator of compromise. An internal host (10.0.0.5) is initiating an outbound connection from an ephemeral port (54321) to an external, non-RFC1918 IP address (198.51.100.20) on a non-standard port (4444). Port 4444 is not commonly used for legitimate services and is frequently associated with reverse shells or command and control (C2) communication by malware, making it a critical security alert.
- ✗
All connections are normal.
Why it's wrong here
This statement is incorrect because not all connections observed are normal. Specifically, the outbound connection from an internal host to an external IP address on port 4444 (10.0.0.5:54321 to 198.51.100.20:4444) is highly anomalous and indicative of potential malicious activity, such as command and control traffic. Therefore, asserting that all connections are normal overlooks a significant security event that warrants immediate investigation.
- ✗
10.0.0.5:3389 to 192.168.1.10:54321
Why it's wrong here
This connection depicts a legitimate Remote Desktop Protocol (RDP) session between two internal hosts. Host 10.0.0.5 is initiating an RDP connection, which typically uses port 3389, to another internal system at 192.168.1.10. The destination port 54321 is an ephemeral port used by the client, while the RDP server would be listening on its standard port 3389. This is common administrative traffic for managing Windows systems within a private network.
Go deeper
Related to this question
Learn chapter
Malware Analysis: Static vs Dynamic
Key term
Reverse shell
A reverse shell is a type of remote access attack where the target machine initiates an outbound connection back to the attacker, allowing the attacker to execute commands on the compromised system.
Key term
Malware
Malware is any software intentionally designed to cause damage, disrupt operations, steal data, or gain unauthorized access to computer systems.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CS0-004 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CS0-004 exam.